The present invention is directed to bicycle transmissions and, more particularly, to an apparatus for assisting a change speed operation in the bicycle transmission.
Various devices have been developed to help reduce the effort needed to operate bicycle transmissions such as derailleurs and internal hub transmissions. Examples of such devices particularly suited to assist the operation of derailleur transmissions are shown in U.S. Pat. No. 5,358,451. The devices shown therein for assisting the operation of a rear derailleur employ multiple moving parts that are in constant motion, thus increasing the amount of moving mass as well as the possibility of premature wear on the components.
The assignee's copending application Ser. No. 10/190,461 discloses an assist mechanism for a bicycle transmission that overcomes such problems. More specifically, that application discloses an assisting apparatus for using power from a rotating member to assist the operation of a bicycle transmission, wherein the assisting apparatus comprises a mounting unit; an input transmission member coupled to the mounting unit, wherein the input transmission member moves between at least a first input position and a second input position; and an output transmission member coupled to the mounting unit, wherein the output transmission member moves between at least a first output position and a second output position. A rotating member engaging member moves between a rotating member engaging position and a rotating member disengaging position, and a motion transmitting mechanism transmits motion from the rotating member engaging member to the output transmission member. A switching mechanism moves the rotating member engaging member between the rotating member engaging position and the rotating member disengaging position in response to movement of the input transmission member and the output transmission member.